The sensitivity of intracellular sodium accumulation to tissue damage in spinal cord injury: a multi-parameter study

Spinal cord injury (SCI) is a complex mechanism, involving not only structural tissue damage but also a disruption in the metabolism of tissue. One such disruption is an accumulation of sodium (salt), which affects how the nerve cells will grow back. The use of sodium blockers (i.e. medicines that help preventing this accumulation) is therefore being recognized in SCI but a method to non-invasively measure sodium in the cells has not yet been developed.

Hypothesis

This study aims to develop a new method to measure intracellular sodium in spinal cord injury (i.e. the salt inside the cells of the tissue), using MRI techniques. This will help us to understand the impact of sodium accumulation on patient disability.

Methods

In order to measure intracellular sodium and its effect on cells functioning, patients will undergo three special types of MRI exam. The first is a sodium magnetic resonance spectroscopy (MRS) scan, where they measure how much sodium there is in the spinal cord overall (total sodium). As this is a combination of sodium inside and outside the nerve cells, they will run a second type of scan called diffusion MRI to measure the fraction of space taken up by the nerve cells. The team believes combining the sodium MRS and diffusion MRI will allow us to determine how much sodium there is just within the cells, which is the sodium that can impair cell regrowth. A third scan known as 1H-MRS will allow them to measure other factors that may damage the cells, such as Glutamate, which is important for the functioning of the cell in passing signals and information, and is known to be also affected by sodium increases inside the cells.

Expected results

They expect higher levels of intracellular sodium to be associated to increased disability in SCI. Increased intracellular sodium could trigger a cascade of other events causing an increase in glutamate concentrations.

Potential application

Determining the source of higher sodium levels in SCI will help understanding its role in disability and secondary injury in SCI. This will ultimately help identifying new targets for treatment. Furthermore, sodium MRI might be a new way to test the effectiveness of new treatments such as sodium blockers, by imaging changes that underpin disability from SCI.